1. Field of the Invention
The field of this invention is a method and apparatus for opening and decoding lock mechanisms. More particularly, the invention is an apparatus or tool set for opening and decoding side bar lock mechanisms that utilize wafer type tumblers. Lock mechanisms of this type have been manufactured for many years by the Briggs and Stratton Company, and they are used on many General Motor Corporation cars.
2. Description of the Prior Art
A side bar lock mechanism of the wafer tumbler type is illustrated and described in U.S. Pat. No. 4,185,482, issued to William B. Nail. The Nail patent discloses a tool that allegedly can be used for determining the bittings of a key that will open a side bar lock employing wafer type tumblers. The Nail device can also be used for opening such locks when a key is lost. The lock mechanism disclosed in the Nail patent has only five (5) wafer type tumblers whereas modern lock mechanisms as used in General Motor automobiles employ six (6) tumblers with a fixed spacing along the longitudinal axis of the lock mechanism, but only five (5) different tumbler positions. Information as to the spacing of the tumblers, the number of tumblers employed and other dimensions of the lock mechanisms for General Motor's automobiles are available to professional locksmiths. The only information that is not readily available to a locksmith is the position that each tumbler must occupy for opening a particular lock. Even information as to tumbler depth or alignment is available if the locksmith has the identification number of the lock.
There can be relative rotation of the parts of locks of this type when the V-notches in the tumblers are aligned so as to accept a leading end of the side bar. This allows the side bar to retract into the lock cylinder under the urging of a spring and thereby permit rotation of the lock cylinder relative to the cylindrical casing in which it is mounted. The V-notches are normally aligned by the key so a lock-picking tool to readily accomplish this same function when a key is lost is needed. It is also very desirable to be able to replace the lost key, so it is important to provide a tool capable of providing information for this purpose.
A locksmith can make a new ignition key for a General Motor's automobile if he knows the idenitfication number of the lock. However, most owners do not have this information, and it is becoming more difficult to obtain the information from the automobile dealer, even when known, who sold the automobile when new. Some dealers no longer retain this type of information. The ignition lock identification number is usually found on the casing of the ignition lock mechanism, but access to this number is not a simple matter when the ignition is locked and the key may be lost. Gaining access to the number requires removal of the steering wheel and other apparatus associated with the steering column locking device, so this approach can be expensive and time consuming for the automobile owner.
One approach utilized to open a side bar lock is to drill the lock cylinder so that a wire or pin can be inserted into the lock in a position to exert considerable radially inward pressure on the side bar. This causes the leading edge of the side bar to bear against the tumblers with more pressure than normal, so when a locksmith manipulates each tumbler with a pick, it is easier to align the V-notches in the tumblers with the side bar so that the lock can be opened. Of course, the problem with this approach is that the lock is ruined by the drilling and must be replaced. If the lock is ruined in an automobile door, then replacing the lock is a labor-intensive and expensive job because the inside door paneling, handles and controls must be removed to gain access to the interior.
There are also rocker type tools which can be used to pick side bar locks. These tools have arcuate-shaped picking sections that are inserted into the lock and rocked up and down while attempting to turn the lock cylinder in its casing. If a locksmith is fortunate, he may open a lock after using one of these tools for awhile. More often than not, he will spend considerable time trying these tools, and then have to resort to some other method such as drilling to open the lock.